Non-covalent interactions – Ion pairing

Question text:

Protein X, a cytoplasmic protein, is folded into its tertiary structure, surrounded by water molecules (red and gray).  This environment has a pH of 7.4.  The blue line represents the protein X backbone.  Some, but not all, of the amino acid side chains are shown in chemical notation.

ProteinX Ion Pairing

The amino acids shown are:  (A) serine, (B) glutamine, (C) leucine, (D) aspartate, and (E) lysine.


Sometimes, a mutation occurs that substitutes aspartate (blue highlight) with alanine (below).


a.   Do you predict that such a mutation would affect the non-covalent interaction pointed to by the arrow?

Yes, the interaction would be affected.

No, the interaction would not be affected.


b.   Provide a scientific explanation to support your prediction.


c.   Predict any new non-covalent interactions that might occur with such a mutation, and provide scientific explanations of them.

Background information:

This question was developed by Paula Lemons' BioSTEPs research group at the University of Georgia with funding from NSF DRL 1350345.

This item was originally designed to be administered electronically.  Only Parts A and B were shown on the initial page.  When continuing to the next page, if the response for Part A was “Yes,” the problem was displayed again, along with the responses entered for Parts A and B, and Part C was displayed.  If the response for Part A was “No,” that was the end of this question.



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This material is based upon work supported by the National Science Foundation (DUE grants: 1438739, 1323162, 1347740, 0736952 and 1022653). Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.